1. Field
The present invention relates to an apparatus that discriminates a vehicle on the basis of a shot image of the vehicle by using information processing technologies.
2. Description of the Related Art
Japanese Laid-open Patent Publication No. 2000-149181 discusses a traffic flow measurement system that includes a camera for acquiring continuous images by successively taking pictures of a road surface and a vehicle that passes a set area on the road surface; a luminance histogram calculation means for obtaining a luminance histogram for each of the continuous images through calculation; a difference calculation means for calculating differences of time-series of the luminance histograms; a saving means for saving the luminance histogram that does not vary for a fixed time as road surface data; a difference calculation means for calculating, when the luminance histograms vary during the fixed time, a difference between two preceding and subsequent luminance histograms; and a vehicle detection means for discriminating the existence of a vehicle by comparing the difference with a preliminarily set threshold. The traffic flow measurement system extracts a moving object in a moving image by using a difference method and performs pattern matching thereon to determine whether it is a two-wheeled vehicle. This technology may not be applied on a still image.
Japanese Laid-open Patent Publication No. 2002-8186 discusses a vehicle type identification device that includes a profile line extraction means extracting a profile line of a vehicle by differentiating image data of the vehicle to be identified; a feature quantity extraction means extracting a feature quantity of the profile line extracted by the profile line extraction means, by calculating the frequency of component in a specified extracting direction of the profile line in the specified area; a storage means storing a previously acquired reference feature quantity of a vehicle, which is an identification reference, and the information indicating a vehicle type in the state of being related to each other; and a feature quantity matching means identifying the vehicle type of the vehicle to be identified, by matching the feature quantity extracted by the feature quantity extraction means and the reference feature quantity stored in the storage means with each other. The vehicle type identification device extracts a profile line of a vehicle and a feature quantity of the profile line then matches the feature quantity with a previously acquired reference feature quantity to identify a vehicle type. This technology may not be effective for a small vehicle such as a two-wheeled vehicle.
Japanese Patent No. 3453952 discusses a traffic flow measurement instrument that includes an image input means that holds an input on-road image obtained from a television camera; an image analyzing means that analyzes a luminance distribution of the on-road image; a vehicle tracing means that traces a vehicle by performing pattern matching on a template segmented from sequentially input on-road images; a vehicle determination means that calculates a tracing distance of the vehicle on the basis of the result of the pattern matching and, when a value of the calculation result is larger than a predetermined value, determines that it is a passing vehicle; a vehicle type determination means that, when it is determined to be a passing vehicle, differentiates an image in a previously determined vehicle type determination area in a vertical direction, that projects the differentiated image in a horizontal direction to acquire added waveform, that selects two peaks of the waveform, which are located farthest from each other, that registers two templates on the basis of a coordinate in the vertical direction of each of the selected two peaks, that calculates a projected length, which is obtained by projecting a vehicle front end portion on a road on the basis of a difference between the two templates in center coordinates, that determines the height of the vehicle on the basis of the rate of change in the calculated projected lengths at multiple points, and that determines the type of the vehicle on the basis of the determined height. The traffic flow measurement instrument recognizes a vehicle by pattern matching to trace the vehicle on the basis of a template segmented from a moving image. This technology may not be applied on a still image.